Constant band width receiver



pri 30, 1935. .1. 1 BoNANNo CONSTANT BAND WIDTH RECEIVER Filed Agg. 20, 1929 To fusse-aufm HMPL/F/Ee sr ,4 R40/0 FREQUENCY INVENTOR JOSEPH L. BONNNO BY 2 ATTORNEY Patented Apr. 30, 1935 i Y UNITEDSTATEYS PATENT OFFICE Joseph L. BonannmForest Hills, N. Y., assignor i Y to Radio Corporation of America, a corpora- Y tion ofDelaWare Application August 2o, 1929, serial No. 387,149

' 9 claims... (Gruss-44)' My present invention lrelates to couplings for pling between radio stages being'secured by varadio circuits, and, more particularly, to a methriable capacity means, Athe inductance coils in od of, and means for, maintaining a constant eachstage'and the capacitive coupling between bandwidthin a radio receiver. vcoils being so designed that the over-al1 coupling '5 In my co-pending application, Serial No. between stages may be brought to zero, or even v5 387,148 filed August 20, 1929, there has been disreversed in phase, at any setting of the Variable closed a system of coupled circuits-f in which capacitive coupling. Y capacity coupling is employed. The capacity Other objects of the invention are to improve coupling in the said system 'is obtained by emgenerally the simplicity and efliciency of couploying auxiliary rotor plates secured to the plings, and to provide a` coupling for radio cirl0 usual rotor shaft of the bath-tub type of gang cuits which is reliable in operation, follows 'a condenser, the auxiliary plates being insulated predetermined law of variation through a given from the rotor shaft. As shown inthe said cofrequency rangeg'and is capable of adjustment to pending application the auxiliary plates are elec- `a sufficientlyv small minimum capacity where the trically connected with each other, and are 'so couplingis capacitive and the range of capacity 15 shaped, and disposed relative to the end stators required is quite large. f of each -sectional condenser in the gang con- The novel features which I believe to be chardenser, that rotation of the rotor shaft not only acteristic of my invention are set forth in partunes the receiver stages, but simultaneously vaticularity in the appended claims, the invention ries the capacity between the said end stators itself,`however, as to both its organization and 20 ofthe tuning condensers in such a manner that method of operation will best be understood by a constant band vwidth ismaintained throughreference to the following description taken in out a given frequency range. connection with Vthe drawing in which I have It is to be understood hereinafter that theexindicated diagrammatically va circuit organizapression constantband Width refers to the tion whereby my invention may be carried into 25 constancy of width of the accepted, or selected, effect. desired band of frequencies throughout the fre- In` the drawing Fig. l schematically shows a quency range of a radio receiver; In other words, circuit employing capacitive coupling between the short expression, constant band width is stages, as disclosed in the copending application employed herein to describe the character of the referred to above, i f

band transmitted through a receiver provided Fig. 2 is a diagrammatic View of the type of with a band pass tuning network. This selected circuit shown in Fig. 1, embedyi'lg my DTeSeIii? band of frequencies vhas the samek width at all invention, f Y times regardless of which portion of the broadF Fig. 3 is a view of a detail, partly in section, of

cast' frequency range .the receiver is tuned to. the invention,

However, the range vof capacity required for Fig. i is a side elevation of Fig. 3, lookingin constant band Width in the usual broadcast re-V the' direction of the arrow( ception receiving circuitmay be quite large. Ac- Referring 130 JChe aeeempauying drawing in cordingly, unless mechanical complications are which like characters of reference indicate the 40 resortedto, it is diicult to secure Aa'suiiiciently Same partsin the differentgures, there is sche- 40 small minimum capacity. Now, I have devised matically shown in Fig. 1 a receiver circuit, as a method and means whereby it is unnecessary diSClOSed in my Said (3o-pending aDDlCatOD. I to resort to mechanical expediencies in order Will Only briey deSCIbe this Circuit, aS the Seme to overcome the aforementioned d iiculty.V iS Clearly diSClOSed in Said appliea'el- Accordingly, it is one of the main objects of The grounded antenna CirCuit'A, G. iS Coupled, 45 my present invention to provide a receiver Yciras at M, t0 2 COIlVeIllOual- TudlO flequelley umcuit in which constant'band width is maintained plfle, Jdie Output 0f the letter being Capeetvely throughout a givenrange of frequencies, a sufli-v Coupled t0 the input 0f a Subsequent stage and ciently small minimum capacity being secured translating device. The .coupling includes coil without resorting to mechanical complications, L1 Shielded aS ai? T1, a C011 L2 Shielded aS ai? T2, 50

regardless of the fact that the range of capacity and a tuning gang COIIdelSel S0 COllueCied berequired may be quite large. tweenA the coils that each condenser section .of

Another important object of the 'invention 1 is the gang, is shunted across its respective coil, the to maintain a constant band width in a receiver adjacent endv stators of rthe condenser sections including a plurality of radio stages, the couproviding the capacity Cc.

The latter is varied by means of a special plate, or plates, mounted to rotate with the rotor shaft of the gang, and designed to vary the coupling between stages simultaneously with tuning of the stages, the variation being such as to maintain a constant band width over the entire desired frequency range.

Where the range of capacity is quite large, it is possible to secure a sufciently small minimum capacity by an arrangement as disclosed in Fig. 2. A few turns of wire are added to the coils L1 and L2, as shown at A and B. Thus, if points A and B represent the ends of'v the Acoils L1 and L2 in Fig. 1, these points are connected and grounded as shown in Fig. 2. 'Y

Ihe end of coil L1 (that is, coil L1in Fig. 2, represents coil L1 in Fig. 1 plus a few turns) Vis connected to the capacityV Cc, through a small fixed capacity Cn. The end of coil Lz is connected to the opposite side of capacityC'c through a small capacity'Cn.

. The variablecapacity C@ is secured by mounting special rotor plates on the common rotor shaft of condenser C1 and C2, and employing these plates to vary the capacity between end stators of adjacent section condensers, as disclosed in my said co-pending application.

In Figs. 3 and 4 is shown the manner of varying the capacity coupling CcY simultaneously with the tuning means, such means being substantially similar to Figs. Lland 4a, ofmy aforementioned co-pending application, Serial No. 387,148, filed August 20, 1929. Briefly, thisv means comprises the usual gangy condenser common shaft 2 which f' Vhas mounted on it a plurality of rotor'plates R1 of one condenser section, and a plurality of rotor plates R2 of an adjacent section. The stator plates S1 and vS2 mesh withr their respective rotor plates. V Y

The metallic housing l, of the, well known bath-tub design, is to be understood as supporting the rotatable metallic shaft 2 Vinvmetallicbearings, 'not shown. The plates R1 and R2 are, of course, electrically connectedtothe shaft 2, thereby grounding them.- A metallic, shielding partition 5 is disposed between the adjacent end stator plates 9 and Ii! of theadjacent condenser sections. The normal electro-static coupling between the plates 9 and ii) is, therefore, practi cally zero, due to the groundedpartition. The stator-plates S1 and S2 Vof each section are, of course, insulated vfrom the metallic housing by spacers 2 of any well known type of insulation material. Y

The normal capacity coupling Cc, between the adjacent end stators 9 and lil being Zero, the coupling may be increased, and made anydesired value by the auxiliary metallic rotor plates P1 and P2 mounted on shaft 2. Thus, between the end stator of each condenser section and the partition 5 is disposed an auxiliary plate. Both plates P1 and P2 are electrically connected Aby .a metallic sleeve 6', the sleeve being insulated from the shaft 2 by the cylindrical insulator bushing 6.

In Fig. l there is shown the relation between the areas of the partition 5, the plates P1 andPz, and the stator plates 9 and lll. All the capacity coupling is determined by the `plates P1 and P2, and, thus, by proper design any predetermined band width can be transmitted between the amplifier stages,'and in this casea constant band widthl is maintained throughoutthe frequency range,

The over-all coupling between stages, at any position of condenser C@ maybe brought to yby 0.9 micro microfarad. This results in is 1 micro microfarad, and a value of one tenth this amount is desired for maintaining a con-` stant band width, the condensers Cn and Cn are adjusted until the over-all coupling is decreased v a net coupling of 0.1 micro microfarad. Y

'The condensers Cn and Cn are employed to retain symmetry of the circuits, i. e., tuning line-up. By over-all capacity is meant all coupling Vcapacity due to the wiring, the coupling capacity Cc and the condensers Cn and Cn. The fewer the number of turns added to each coil L1 and L2, the: larger can the capacities C11 and Cn be; thus, facilitating adjustment.

While I have indicated and described a system for carrying my invention into effect, it will be apparent to one skilled in the art that my invention` is.v by no means limited to the particular organization shown and described, but that many modifications inthe circuit arrangements, as well as inthe apparatus employed, may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim is: f i

1. A method of operating adjacent tuned radio stages through a predetermined range of frequencies which consists in capacitively coupling the adjacent stages,varying the coupling simule taneously with the tuningof said' stages, and adjusting. thev overall coupling capacity to a minimum.v Y I a 2. A method Vof operating a plurality of tuned radio stages lthrough a predetermined range of frequencies which consistsV in lcapacitively coupling said stages, varying said coupling simultaneouslywith the tuning of said stages, the cou-4 pling variation being such that a constant frequencyband width is received at any frequency Withinsaid range, and maintaining the over-,al1 coupling capacity at a. minimum foreach frequency. l

3. A receiver comprising a plurality of radio stages, means for tuning each of said stages, means for coupling adjacent stages. meansjior varying the `coupling between adjacent stages simultaneously with variation of said. tuning means, the coupling variation being such that a. constant frequency band width is received over the tuning range and 4additional adjustable means electrically connected between adjacent stages for reducing the over-all couplmg characteristic to a minimumfor a given frequency.

4. VIn a' receiver, as dened in claim 3, said additional means being capacitive, said stages being additionally conductively connected.

5. In a receiver, a plurality of radio' stages, means for tuning each of thestages, each of said stages including an inductance, said inductances being directly connected, meansV for capacitively coupling the stages, said .coupling means being variable with the tuning means, the coupling vnriation being such that a constant frequency band width is :received over the tuning range and additional capacitive means electrically connected between said stages for reducing the oyerall'couplingv characteristicvto a minimum fory a, given frequency. Y 6. In combination, in a tunable vradio frequency band pass network, a pair ,of resonant oscillationcircuits each including a coil and a. variable tuning condenser, a common operating shaft for the rotors of both'condensers, means,

operative with said shaft, for regulating capacity coupling between the circuits provided by inter-electrode capacity between said condensers, and fixed auxiliary condensers connected between said circuits for neutralizing a desired portion of said coupling capacity.

7. In a receiver, a source of radio frequency signal energy, a succeeding signal transmission network, said network including at least two tunable signal circuits, each circuit including an adjustable tuning reactance, an adjustable reactance for coupling the tunable circuits, a common means for adjusting said coupling reactance with the tuning reactances in such a man- 15 ner that a substantially constant signal frequency band width is transmitted through said network over the receiver tuning range, and additional means for securing a sufficiently small minimum coupling reactance value between the tunable circuits when said range is small.

8. In a receiver as dened in claim 7, said additional means comprising a pair of auxiliary reactances of the same sign.

9. In a receiver as dened in claim 7, said additional means comprising a pair of auxiliary reactances which are independent of said adjustable coupling reactance but of the same sign as the latter.

JOSEPH L. BONANNO. 

